1. Field of the Invention
The instant invention generally relates to a method of embedding material in a glass substrate. More specifically, the instant invention relates to a method of flowing a glass composition into a recess in a patterned surface of a mold substrate formed from the material to form a glass substrate, with the resulting glass substrate having the material of the mold substrate embedded therein.
2. Description of the Related Art
The field of electronic microsystems covers a broad array of technologies that benefit from functionality of electronic devices but in which minimal size is desired. For example, implantable devices, batteries, integrated circuits, microfluidic circuits and associated devices such as pumps and valves represent a few technologies that benefit from advances in the field of electronic microsystems. There is a constant drive to make advances in the field of electronic microsystems that enables further minimization in size while retaining or improving the functionality of the electronic microsystems.
Electronic microsystems commonly employ an architecture of electrical components and insulative components. Due to the small profile of the electronic microsystems, the insulative components serve a vital function of electrically separating the electrical components to enable proper function. However, there is often a need to convey electrical signals between electrical components that are separated by insulative components. In this regard, there is a strong desire to employ electronic feedthroughs or vias that pass directly through the insulative components, rather than traveling around the insulative components. The electronic feedthroughs or vias provide the benefit of shorter wire lengths, which results in lower resistive loss and lower consumption of precious space in the electronic microsystems as compared to usage of longer wire lengths that would be required to travel around the insulative components. There is also a desire to incorporate devices into the insulative components to maximize insulation thereof and to further conserve space in the electronic microsystems.
Glass is an ideal material for use in electronic microsystems due to excellent electrically insulative properties thereof, as well as biological neutrality and low coefficient of thermal expansion. However, formation of electronic feedthroughs or vias in glass is particularly problematic in the field of electronic microsystems and has often led to a preference for polymeric materials for use in the insulative components. Electroplating of vertical feedthroughs in glass is known in the art. Existing processes such as sand blasting, ultrasonic drilling, electrochemical etching, laser drilling, RIE etching, and mechanical drilling have been used to generate holes in the glass for purposes of accommodating the vertical feedthroughs or vias. Due to the extremely small dimensions of the holes, traditional glass molding techniques are not considered. The aforementioned processes used to generate holes in the glass suffer from drawbacks such as an inability to achieve sufficient spatial resolution with sufficient repeatability, propensity to damage the glass or alter the surface thereof in an undesirable manner, limitations as to the size of holes that can be generated, and/or limitation to batch mode processing.
Methods of structuring wafers comprising glass and silicon regions have been suggested in the art. Such methods include the step of structuring a surface of a flat silicon substrate to obtain recesses therein. A flat glass substrate is then anodically bonded to the structured surface of the silicon substrate under vacuum to at least partially cover the structured surface of the silicon substrate. The glass substrate and the silicon substrate are then tempered in such a manner that the glass is heated above a reflow temperature thereof and flows into the recesses of the structured surface of the silicon substrate with the aid of vacuum pressure in the recesses, which acts to draw the glass into the recesses. The glass is then resolidified, and material is removed from the resolidified glass region in such a manner that the resolidified glass region assumes a surface which is flush with the structured surface of the silicon substrate thereby forming a wafer. In this regard, features of the structured surface of the silicon substrate extend through the resolidified glass region. Material may also be removed from a rear side of the silicon substrate to expose the resolidified glass region in certain areas to further thin the wafer. In this regard, the resulting wafer can be structured to include the glass and silicon regions. The combined thickness of the resulting glass and silicon regions that are bonded together is typically between 0.1 to 1 mm. However, wafers that comprise glass and silicon regions formed through the process as described above are extremely fragile and generally cannot be thinned below the thickness of 0.1 mm without fracturing due to insufficient adhesion between the glass and silicon regions. While portions of the wafers may be salvaged, fracturing is undesirable and complicates additional processing steps. Furthermore, it is difficult to obtain adequate flow of the glass into recesses having a width of less than 100 μm.
Given the ongoing drive to minimize components of electronic microsystems that can make use of glass substrates having material embedded therein, there remains an opportunity to further develop methods of structuring such glass substrates that enable smaller thicknesses of the glass substrates to be achieved while maintaining the bond between the electrically-conductive material and glass such that the glass substrates remain intact at thicknesses of less than 0.1 mm. There also remains an opportunity to minimize feature sizes of the material embedded in the glass substrates while enabling enhanced flow of the glass into recesses during embedding of the material in the glass substrates.